In recent years, stand-type flat display apparatuses with a display screen comprising an LCD (liquid crystal display), a plasma display, or an EL (electronic luminescence) display, are becoming increasingly common. In particular, there is an increasing need for large-sized stand-type flat display apparatuses equipped with a display screen size of 30 inches or larger. A variety of such products have been developed for household or business purposes.
In these stand-type flat display apparatuses, a display screen unit includes an LCD, plasma or EL display, and a main body unit includes an amplifier unit, power supply, drive circuit and other devices. The display screen unit and the main body unit are typically supported by a stand including a leg extending horizontally such that the display screen unit stands substantially vertically with respect to the floor. The stand further includes a rotation mechanism by which the main body unit can be axially supported in a freely rotatable manner.
FIG. 1 shows an elevational view of an example of the above-described stand-type flat display apparatus. A flat display apparatus 100 is a console-type flat display apparatus including a display screen unit 110, a main body unit 120, and a stand 130. The term “console type” refers to the type of flat display apparatus in which the main body unit 120 is composed of a control unit 121 including a power supply, a drive circuit and a control circuit and an amplifier unit 122, and in which the main body unit 120 is integrated with the display screen unit 110.
The display screen unit 110 includes a display screen 111 such as an LCD, plasma or EL display. The main body unit 120 includes the control unit 121 and amplifier unit 122. The main body unit 120 is integrated with the display screen unit 110 and axially supported by the stand 130. The stand 130 is comprised of a stand support column 131 and a stand base 132. The stand support column 131 has a rotation mechanism by which the main body unit 120 can be supported in a freely rotatable manner.
(1) As an example of the rotation mechanism for the above-described stand-type flat display apparatus, JP Patent Publication (Kokai) No. 08-331485 A (1996) discloses a rotation mechanism for television sets. In this rotation mechanism, sliding rollers 7 are disposed at ends of each side of the bottom of the television main body unit for supporting the weight thereof and allowing the same to be rolled. The sliding rollers 7 are adapted to roll on the upper surface of a television stand 13, thus allowing the television main body unit to be rotated.
It is difficult, however, to apply this television rotation mechanism to the rotation mechanism for the stand-type flat display apparatus. This is due to the fact that the aforementioned mechanism, in which the television main body unit and the rollers are adapted to roll, requires certain width and depth in the television main body unit and the television stand. Further, it creates a gap between the television main body unit and the television stand and thus exposes the inside of the television stand as the television main body unit is rotated.
(2) Referring to FIG. 1, the display screen unit 110 includes the display screen 111 such as an LCD, plasma or EL display. The main body unit 120 includes the control unit 121 and amplifier unit 122. The main body unit 120 is integrated with the display screen unit 110 and axially supported by the stand 130. The stand 130 is composed of the stand support column 131 and stand base 132. The stand support column 131 has a rotation mechanism by which the main body unit 120 can be supported in a freely rotatable manner.
As a conventional example of this rotation mechanism, JP Patent Publication (Kokai) No. 10-32771 shows a rotation mechanism in which a support column 7 supporting a display 3 and a rotation platform 2 are supported on a base 1. A thrust bearing 8 is disposed between the base 1 and the rotation platform 2 in order to allow the display 3 to be rotated.
If this rotation mechanism were to be applied to the stand-type flat display apparatus, a structure would have to be adopted such that the display screen unit and the main body unit are axially supported by the support column of the stand in a freely rotatable manner.
(3) In the stand-type flat display apparatus as shown in FIG. 1, the rotation mechanism in the stand 130 is typically equipped with a drive motor, for example, to allow for an automatic rotation of the display screen unit 110 and the main body unit 120.
In this type of automatic rotation mechanism, a means is provided to reduce the rotation output of the drive motor at a certain reduction ratio. Specifically, a certain amount of load is put on the rotation axle being rotated so that the rotation can come to a stop when the drive motor is stopped. By appropriately selecting the reduction ratio, the automatic rotation speed can be controlled. For example, a winch mechanism is commonly provided in the worm unit connected to the drive motor.
Similar rotation-speed reduction mechanisms in conventional display apparatuses are disclosed in JP Utility Model Publication (Kokai) No. 63-61884 A (1988) and JP Utility Model Publication (Kokai) No. 64-31246 U (1989).
The former, JP U.M. Kokai 63-61884, discloses a rotating cabinet in which a cabinet main body unit is placed on a pedestal in a freely rotatable manner. A bevel gear and an output gear are adapted to be engaged due to the weight of the cabinet main body unit, and a reducing gear train is arranged in a vertical direction and is driven.
The latter, JP Utility Model 64-31246, discloses a turning mechanism comprising a gear that receives the rotation of a gear mechanism, a bevel gear adapted to resiliently engage the gear on the axis side, and a clutch mounted on an upper platform in such a manner as to engage the bevel gear. In this turning mechanism, the gear mechanism and the motor are protected from damage in the event of an excessive load torque.